Only Half Human - Nathaniel Wright - Bog

High school was hard enough for Lesley Robinson, and that was before she sprouted wings, a tail, and devil horns. She and her witch mother are forced to flee to Misty Hollow, a hidden haven for mythical creatures. As the only half-demon at her new school, Lesley struggles to fit in. Desperate to restore her humanity, she can't help but be tempted when Asmodeus, chief prince of the demons, gives her a magic necklace with the power to turn her human again. But there's a catch-it won't work without the right spell, and he won't teach Lesley the spell unless she sells him her soul.